1. Field of the Invention
The present invention relates to a semiconductor device. In particular, the present invention relates to a semiconductor device having a capacitor.
2. Description of the Related Art
Recently, there have been advanced the research and development of ferroelectric memory (FeRAM: Ferroelectric Random Access Memory) using ferroelectric film as a capacitor dielectric film.
A Pb(ZrXTi1-X)O3 film (PZT film) or an SrBi2Ta2O9 film (SBT film) is given as a typical ferroelectric film used for the ferroelectric memory. PZT is a perovskite compound, and the SBT is a Bi aurivillius phase compound having a pseudo perovskite structure.
If a PZT film is used as the ferroelectric film, a conductive perovskite type metal oxide film, such as an SrRuO3 film (SRO film), is used as the electrode to improve the fatigue characteristic. For example, JPN. PAT. APLLN. KOKAI Publication Nos. 2000-208725 and 2000-260954 disclose a ferroelectric capacitor using a stacked film of SRO film and Pt film as the electrode.
However, it is not easy to form a PZT film of good crystallinity and orientation on the SRO film formed on the Pt film. For this reason, it is difficult to form a capacitor, which is excellent in imprint and retention characteristics and has high reliability. The foregoing problem generally occurs in the combination of conductive perovskite type metal oxide film and noble metal film (or noble metal oxide film) in addition to the combination of SRO film and PT film.
As described above, stacked structure of the conductive perovskite type metal oxide film and the noble metal film (or noble oxide film) is applied to the capacitor electrode. In this case, it is difficult to form the conductive perovskite type metal oxide film having preferable crystallinity. Thus, it is difficult to form a dielectric film, such as PZT film, excellent in crystallinity. As a result, there is the problem of remarkably reducing capacitor characteristics and reliability.